Recombinant human thyrotropin (rhTSH) is being evaluated for diagnostic use in patients with thyroid cancer. rhTSH has potential application for administration to patients with thyroid cancer on suppressive levothyroxine (LT4) prior to radioactive iodine (I-131) scans and thyroglobulin measurements. The desired goal is to detect post thyroidectomy remnants, persistant or recurrent well-differentiated thyroid cancer and metastases while patients remain clinically euthyroid.